What an animal needs in its feed

All animals and humans need the nutrients called carbohydrates, proteins, fats, vitamins and minerals in their feed in order to stay healthy, have energy, grow and reproduce.

Carbohydrates such as sugar and starch are burned in the body to give energy. Fats are broken down in the body to give carbohydrates and water. Animals and humans store carbohydrates as fat in the body.

Protein forms the building blocks of the body. It is needed to produce the muscles.

Minerals such as copper and calcium are needed to form the bones, brain, nerves and blood. Plants take in minerals from the soil. Vitamins are essential for a healthy body and all plants contain several vitamins.

If animals do not get enough of any nutrient they will become less productive and may die from a condition called a deficiency disease.

If an animal does not get enough fat, protein or carbohydrate in its feed it cannot grow properly, loses weight, milk production drops and production of young is affected. Lack of minerals results in such problems as failing to come into heat, poor bone growth and loss of hair or wool. While lack of essential vitamins can cause problems such as blindness and swollen joints.

Water

Animals need plenty of fresh clean water every day. Always give water before feeding animals and allow them to drink at least three times a day. Ruminants on pastures can be watered every 2 – 3 days. Do not allow animals to stand in the water at the drinking place. This can cause disease to spread. Water needs will vary according to the feed they eat and the weather.

A pinch of salt can be added to the drinking water to provide minerals.

New methods of feeding animals have been developed and are used in many countries:

Feeding urea-treated straw. Straw is a low nutrient feed for ruminants but if it is wetted with urea and covered for a week it becomes more nutritious.

Molasses-urea-mineral blocks. Blocks made of molasses, mineral salts and urea are a good supplement for ruminants which lick the block and take in the nutrients.

Milk is produced in the udder from nutrients in the blood which flows through the vessels (tubes) in each quarter. The greater the amount of blood passing through the udder the greater the amount of milk which is produced. The milk is released as the teat is sucked or squeezed.

Milking by hand will take from 5 to 10 minutes. The udder should be emptied at each milking and this will stimulate the udder to develop more milk. Always milk the animal quietly. A good time to milk is in the morning before the animal goes out to graze and in the evening. Always milk at the same time each day.

Differences in milk yields

Milk yields will vary for different reasons:

• Some types or breeds of animals produce more milk than others.
• Milk production will be greater after the birth of the second or third young.
•  Extra good feed, minerals and a lot of water are needed by the animal in milk in order to produce milk.
• Milk production improves when the animal gives birth in the rainy season when there is a lot of feed available.
• Talking, singing or whistling to the sheep, cow, goat or buffalo as it is being milked makes it relax and the milk is let down better.

Infection of the Udder (Mastitis)

A good udder is essential for milk production. If the udder is injured or infected milk production can stop. Infection of the udder is called mastitis and is caused by germs. Mastitis can be recognised by:

• The milk is not clean, the colour is different and there may be lumps in the    milk
• The udder is hot, painful and swollen.
• The skin of the teats is cracked.
• The animal may stop eating.

More than one quarter of the udder may be infected. The mastitis may be caused by a germ which is infectious and spreads to other animals. Goat milk must be closely looked at for signs of mastitis because the milk may not show a noticeable change in colour.

To treat mastitis the udder should be bathed with warm water. The bad milk in the udder should then be removed using a clean teat catheter or by hand milking. This is carried out at least twice a day until the udder returns to normal.

A treatment which is now preferred is to bathe the affected quarter with cold water and then milk out the quarter. The udder is then dried and massaged. This is repeated morning and night until the udder returns to normal. If the infection is severe this treatment is repeated every 2 to 3 hours.

Normal Calving

The water bag appears through the vulva. The cow will strain more. The head of the calf will appear and this breaks the bag. You will then be able to see both of the calf’s front feet. It takes 4 – 6 hours for the calving to reach this stage. In heifers it might take longer. As the chest comes through the vagina the calf starts to breathe. It is better to leave the cow alone to give birth naturally. However if you want to help with the calving you can gently pull the calf by its feet. If the navel cord is still attached to the cow you can cut it with a clean sharp knife or a pair of scissors, then put tincture of iodine or alcohol on the end of the navel cord.

Caring for the Cow after Calving

Give the cow clean water to drink immediately after she has calved as she will be thirsty.

The water bag (afterbirth) will come out naturally but you can help to remove it by gently pulling it. The afterbirth should have come away by 24 hours after the birth. If the afterbirth remains in the uterus it will cause an infection and you will need to get your veterinarian to help.

Allow the calf to suckle from its mother as soon as possible so that it takes in the colostrum, the yellowish milk which is produced immediately after birth. The colostrum is rich in protein and protects the calf against disease.

Some people use the colostrum for their food but it is essential to make the calf strong and healthy and should be left for the calf. You must allow the calf to take colostrum for at least four days after its birth.

The female reproductive system consists of two ovaries and a womb. Every so often the ovaries produce very small eggs (ova). The time when this happens is called heat or oestrus. Cattle and buffalo regularly come into heat all year round. Most sheep and goats come into heat at a particular time of the year (breeding season).

When do animals come into heat for the first time?

Animals come into heat when they reach puberty. This occurs at different ages in the different ruminants:

•  Well fed cows and buffalo come into first heat at 10 – 20 months of age.
• Sheep and goats come into first heat between 6 – 12 months of age.

The duration of heat is very short.

• In cows and buffalo it lasts for less than a day.
• In goats heat lasts for 1 – 3 days.
• In sheep heat lasts for 1 – 2 days.

A healthy animal which was not mounted by a male or given artificial insemination will come back into heat. Cattle and buffalo cows will come into heat after 3 weeks (give or take a day or two), and female goats and sheep will come back into heat after 17 days (give or take a day or two).

The Female which does not come into Heat

The female may not show signs of heat because she is too old, or she may have been mated without the owner knowing. Sometimes animals come into heat without showing any signs. This is called a “silent heat” and is common in buffalo cows. If the feed is not sufficient or there is a lack of protein, salts or water, the animal can fail to come into heat. You will need to improve the female’s feed to bring it into heat.

Pregnancy in Ruminants
When the animals mate sperm from the male loins with the eggs in the womb. Heat then finishes and the belly of the female enlarges over several months as the young grow during pregnancy.

Heat stops when pregnancy begins. The animal becomes quieter and the belly grows bigger. In milk animals the production of milk will gradually drop.

Length of pregnancy

If male and female animals have been allowed to run together in a large herd it will be difficult to determine the expected time for birth (parturition). If however you do know when a female was mated or given artificial insemination you can determine when she will give birth.

The length of pregnancy differs in different animals.

There can be a few days difference either way depending on the type, climate, feed and other factors.

Management of the pregnant animal

You must remember that a pregnant animal will need more feed and will benefit from the addition of some grain to the feed towards the end of pregnancy. All pregnant animals should be kept close to home towards the end of the pregnancy and some form of shelter should be provided. They should be watched twice a day for signs that parturition is close. In particular cattle and buffalo need a clean, well ventilated place, preferably with a sand or grit floor on which suitable bedding is placed. Do not keep a pregnant animal constantly tied up or with little room to exercise in. Allow her some freedom in a field or yard each day. She should be observed closely twice a day for signs of parturition.

What is a parasite?

A parasite lives in or on another animal and feeds on it. All animals and humans can become infected with parasites. Ruminants can be infected with several types of worms.

Roundworms are small, often white in colour, and look like threads. Different roundworms are found in all parts of the gut and the lungs.

Tapeworms are long, and flat and look like white ribbons. They consist of many segments and live in the intestine.

Flukes are flat and leaf-like, they live in the liver. Schistosomes are small and worm-like, both infect animals kept on wet, marshy ground as their eggs develop in water.

Infection of Parasites in Animals

The roundworms, flukes and schistosomes lay eggs which pass out of the animal in the dung onto the pasture. Tapeworms produce eggs in the segments which break off and pass out in the dung. Animals become infected when they graze the pasture. Parasites feed on the food in the gut and on the blood of the host. The animal becomes weak and loses weight or does not gain weight. It can develop diarrhoea, which in sheep makes the wool wet and attracts flies.

Eventually the host becomes so weak that it dies. Young animals are especially affected by parasites.

Currently, several minerals are available in chelated form. Among these are magnesium, copper, cobalt, iron, manganese and zinc. Under certain conditions ruminants have responded to mineral chelates, but it is not clear from the studies reported whether this response is due to the form of the mineral or simply to increased mineral consumption. Zinc-methionine may have an advantage in treatment of footrot and its prevention in problem herds, as well as improved immune response in cattle. However, there is limited research to support these conclusions. Copper availability may be low for ruminants in areas where molybdenum and sulfur are high. Providing copper in a form that does not interact with these antagonists would be advantageous, but it is not clear that copper chelates meet this objective.

While chelated minerals may have a special role under certain conditions and in future dairy cattle feeding programs, information presently available does not consistently show advantages for their inclusion in the diet. Also, some nutritionists find it more economical to add more of a nonchelated mineral rather than use a more bioavailable chelated mineral.

Feeding Dietary Cation-Anion Rations in the Prepartum Period

Dietary cation-anion balancing is a new concept that has received much attention in recent years as a nutritional tool for reducing the incidence of milk fever and perhaps retained placenta. Minerals considered in the balancing concept are sodium, potassium, sulfur and chlorine. The ration is fed for about 3 weeks prior to calving.

Trace minerals should not be added to dairy rations indiscriminately. Many rations will contain adequate levels without their addition. If a trace mineral problem is suspected, have your ration tested and make adjustments in the mineral mixture accordingly. Too much of a particular mineral could further antagonize the situation.

Iron

The role of iron in the body is mainly as part of the processes of cellular respiration, as a component of hemoglobin, myoglobin and cytochrome, and in certain enzymes. About 60 to 70% of the iron in the body is found in hemoglobin and 3 to 5% in myoglobin. Traces of copper are required for the utilization of iron in hemoglobin formation.

The need for iron in the diet of the adult dairy cow is estimated at about 100 mg/day. Minimum iron requirement for healthy dairy calves is about 30 mg per day. Calf requirements for dietary iron depends on the iron status of their dam and the calf’s body stores. Calves with high iron stores appear to use those stores in preference to dietary iron, while those with lower stores have a higher requirement for dietary iron. Calves fed an exclusive whole milk diet (milk is low in iron) will develop iron deficiency anemia within 2 to 3 months. This practice is desirable in growing veal calves.

Iron deficiency in most dairy cattle rations has rarely been observed. Deficiency symptoms reported in calves include reduced weight gains, listlessness, inability to withstand circulatory strain, reduced appetite and anemia.

Studies at the Hindustan Animal Feeds show that iron was available to dairy cattle from ferrous sulfate, ferrous carbonate and ferric chloride in decreasing order of availability. Ferric oxide iron was only about 12% as available as the iron from ferric chloride.

Iron deficiency seldom occurs in older dairy cattle unless as a result of severe loss of blood caused by parasitic infestations, injury or disease.

Manganese

Manganese is needed in the body for normal bone structure, for reproduction and for the normal functioning of the central nervous system. It is found stored primarily in the liver and kidneys. Its functions are believed to be in the activation of several enzymes.

Studies with dairy cattle indicate that 40 ppm of manganese in the ration would appear to meet the requirements with a margin of safety. Most dairy rations contain levels of manganese in excess of the suggested requirements. This is especially true where forages are available. Excessive amounts of manganese in the diet increase blood lipids and cholesterol and change the composition of fatty acids in the blood, liver and heart which could affect their normal function.

General symptoms of manganese deficiency include impaired growth, skeletal abnormalities, disturbed or depressed reproductive function, nervous disorders of newborn, and defects in lipid and carbohydrate metabolism.

Copper

Copper is essential to the activity of certain enzymes and, along with iron, is necessary for the synthesis of hemoglobin. It is also an important element for normal immune function. Low copper status may contribute to increased susceptibility to infections such as mastitis. Studies have shown that liver copper stores decrease dramatically in late pregnancy, and reach their lowest point five weeks prior to calving.

A variety of copper deficiencies have been reported, including anemia, retarded growth rate, failure to fatten, loss of body weight, diarrhea, and depigmentation of hair. A characteristic of copper deficiency is a swelling of the ends of the leg bones above the pasterns.

A recent study by Hindustan Animal Feeds showed that 11% of animals on nine dairies were deficient in copper, while 52% had marginal copper status. Only 38% of the cattle had normal copper levels. According to the study, heifers and dry cows in particular had marginal or deficient copper levels in their blood and livers. Some Locational soils are high in molybdenum which is a copper antagonist.

Most data indicate that rations containing 10 ppm of copper are adequate. In areas where rations may be fairly high in molybdenum and sulfate, the copper requirement may be increased two-fold.

Zinc

Zinc is closely associated with a number of enzymes in the body and is a component of the enzyme carboxypeptidase and the hormone insulin. It appears that zinc is required for normal mobilization of vitamin A from the liver. This is verified by the fact that skin lesions and corneal changes in zinc deficient animals are similar to those occurring in animals deprived of vitamin A. In calves, a zinc deficiency has resulted in leg and bone disorders, parakeratosis, impaired vision, and rough and thickened skin.

Zinc deficiencies reported are similar to many other nutrient deficiencies. This observation indicates that zinc is probably involved in the metabolism of one or more nutrients. A number of sources of zinc are available.

Supplemental zinc in organic form has often been beneficial in prevention of, and as a therapeutic aid to, hoof problems of dairy cattle and of foot rot. The role of zinc in maintaining skin tissues and the inflammatory response is probably responsible for this effect.

Cobalt

Cobalt is a component of vitamin B₁₂ and therefore affects blood formation. A nutritional anemia in cattle and sheep living in cobalt-deficient soils has successfully been treated with cobalt. Microorganisms in the rumen of these animals utilize cobalt to synthesize B₁₂.

Adding cobalt and copper to the diet of ruminants has been shown to increase rumen microbial activity and enhance digestion of some forages. A general recommendation for ruminants is 1 mg per day per 1000 lbs body weight. Converted to ppm, a total level of 0.1 to 0.15 ppm in ruminant rations should be adequate to prevent any possible cobalt deficiencies.

Cobalt carbonate has been reported to be a good source of cobalt. Other sources are cobalt sulfate and cobalt oxide.

Iodine

The primary physiological requirement for iodine is the synthesis of hormones by the thyroid gland that regulate energy metabolism. Since iodine functions as a part of the hormone thyroxine and thyroxine is produced by the thyroid gland, a deficiency of iodine causes an enlargement of the gland. Birth of goitrous calves which are sometimes weak or dead and may be hairless is a sign of borderline or definite dietary iodine deficiency even though the cows may appear normal. Milk iodine levels reflect the cow’s iodine status. Goiter may develop in nursing calves as a result of an iodine deficiency in the cows’ diet.

A relationship between thyroid activity and reproductive performance has been suggested. Tennessee workers have reported an improvement in conception rate of repeat-breeder cows by treating with organic iodine 8 to 12 days before the onset of estrus. Also, in one field study the number of retained placentas and irregular breeding intervals was reduced when iodine was added to the ration. Similar results have been reported in Maryland.

The requirement for iodine as recommended by the HAF is 0.6 ppm of the ration dry matter. Iodized salt should contain about .005 to 0.1% iodine. Complete feeds (with CSH, etc.) containing 1% salt that contains .01% iodine in the trace salt will contain 1 ppm in the finished feed. Therefore, salt containing .005% to .01% iodine added to complete feeds at the rate of 1% (20 lb/ton) will meet the nutritional requirements of dairy cows for iodine.

Iodine toxicity can be a problem where herds are fed too much iodine to prevent diseases such as foot root and lumpy jaw. Symptoms observed and reported are tearing eyes, nasal discharge, bulging eyes, nervousness, rough hair coat including loss of hair, sluggish movement, reduced appetite, tracheal congestion that causes coughing, and lowered milk production. Recovery from iodine toxicity is rapid after the excess iodine is eliminated from the diet.

Excessive levels of dietary iodine result in high blood iodine, excretion of large amounts of iodine in urine and feces, and increased secretion into milk. The Food and Drug Administration (FDA) is concerned with high levels of iodine consistently in milk.

Selenium

The importance of selenium in cattle feeding is continuously being evaluated and has been considered an essential element for cattle since 1957. The current recommendation listed by the HAF is 0.3 ppm. However, in 1993 the FDA lowered the maximum selenium allowance from 0.3 to 0.1 ppm, citing concerns over environmental impact of selenium excreted by animals.

The classic deficiency symptoms reported in the literature for livestock are white muscle disease in calves, stiff lamb disease, and muscle degeneration in pigs, and is related to reproductive problems in cattle such as retained placenta. Selenium plays a key role in the immune system, protecting white blood cells from the toxic by-products known as oxidants resulting from the destruction of pathogens. Both selenium and vitamin E are necessary to prevent white muscle disease and for normal immune response in cattle.

Work at Hindustan Animal Feeds Cattle ranch showed that retained placenta may be controlled in herds with a high incidence of this problem by either an intramuscular injection of 50 mg of selenium as selenite and 680 IU of vitamin E given approximately 21 days prepartum; or by feeding a total intake of 1.0 mg of selenium per day as selenite during the last 60 days of the dry period. Since protein feeds are natural sources of selenium, dry cow rations low in protein may lead to increased incidence of retained placenta.

There are many factors which are related to retained placenta. Disease, stress, and nutrition are considered the primary factors related to a high incidence of this problem. In many herds where the incidence is high, the cause or causes need to be determined and eliminated. Diseases should be eliminated by developing a good herd health program with the cooperation of your veterinarian.

Nutritional deficiencies of vitamin A, iodine, selenium, phosphorus and calcium increase the incidence of retained placenta. Nutritional imbalances which have been reported to increase the incidence include an imbalance of calcium and phosphorus and to some degree their ratio. Generally, the ration is of less importance so long as each is adequate. We recommend a ratio range of 1.5:1 to 2:1 of calcium to phosphorus in the final ration.

Other conditions associated with retained placenta include infections, difficult calving, and hormonal deficiencies. Also, retained placenta occurs more frequently during the colder months and less during the warmer months. As usual, high-producing cows seem to be more susceptible than low-producing cows.

There are three sources of selenium available, and selenium concentration varies from one source to another depending on water content. The most concentrated source of sodium selenite (Na₂SeO₄) contains 41.8% selenium while the next most concentrated form (Na₂SeO₄5H₂O) contains 30% selenium. The addition of 307 mg of sodium selenite as Na₂Se₄5H₂O or 220 mg of sodium selenite as Na₂SeO₄ per ton of feed would provide 0.1 ppm of selenium in the ration.

The selenium level of the hair of cattle is a useful indicator of both selenium deficiency and selenium toxicity. Most studies have shown that cattle with hair values consistently below 0.25 ppm probably need supplementation and that over 5 ppm may lead to clinical signs of selenosis.

Selenium toxicity is common in certain parts of the United States where soil selenium concentrations are high. In Florida, however, soil selenium is low and selenium concentrations in Florida grown forage is not a concern. Excessive ingestion of selenium causes alkali disease, sometimes called blind staggers and bobtailed disease due to the loss of the hair from the switch of cattle. Acute selenium poisoning is characterized by dullness, slight ataxia, rapid weak pulse, labored respiration, diarrhea, a characteristic posture, and death due to respiratory failure. Less acute signs include abnormal hoof growth and hair coat. Alkali disease has been observed in animals consuming diets with selenium concentrations in the range of 5 to 40 ppm. Trace minerals are required in minute amounts and therefore difficult to justify mixing by an individual for feeding to a given dairy herd. A few dairymen do, however, have complete and/or trace mineral mixtures formulated to their specifications. In doing so, one must remember that mineral mixtures will need to be updated from time to time to keep pace with major ration ingredient changes. This is especially true with the balance of calcium and phosphorus.

Generally, about 60 to 1000 lbs of a complete mineral is needed per ton of finished feed on a DM basis. The ratio of calcium to phosphorus needed in the mineral mixture varies considerably depending on the ingredients used in the feed.

Blood is sometimes used to determine the adequacy or deficiency of a mineral compound in the ration. The normal values of certain mineral elements reported in bovine blood are: calcium, 10 mg %; phosphorus, 4-6 mg %; and magnesium, 2-4 mg %.

Calcium and Phosphorus

Over 70% of the total minerals in the body are calcium and phosphorus. About 99% of the calcium and 80% of the phosphorus of the body are present in bones and teeth. Bone, therefore, not only serves as an organ of structure, but also as a reservoir of both calcium and phosphorus.

Calcium and phosphorus are closely related elements and are laid down in bone in a ratio of 2.2 parts calcium to 1 part phosphorus. This means that a deficiency or an overabundance of either mineral could interfere with the proper utilization of the other. An imbalance of either mineral can cause them to bind with each other and become unavailable to the animal. Studies have also shown that phytate phosphorus, the major form of organic phosphorus occurring in plants, is generally available to the ruminant unless the concentration of calcium in the diet is very high. Utilization of other minerals such as magnesium may also depend on adequate calcium and phosphorus nutrition.

The importance of calcium and phosphorus in dairy rations has been recognized for several years. For a period of time, more minerals were frequently added to the ration than needed. With the adverse publicity about phosphorus getting into lakes and streams, dairymen are now more concerned about having an adequate but minimum amount of phosphorus in the ration. Fecal excretion of phosphorus does depend on the amount of phosphorus in the diet, and it has been shown that for every g/d decrease in phosphorus intake fecal excretion decreases by 0.55 g/d, while for each g/d increase, fecal phosphorus increases by 0.8 g/d.

No longer can we consider only the concentrate and ignore such important feeds as silage, hay and outside mineral mixtures. Availability of the minerals in a forage depend on forage type. As an example, studies have shown that absorption of calcium from corn silage-alfalfa hay diets was higher than when alfalfa was fed alone. Although alfalfa is higher in calcium than corn silage, calcium in alfalfa appears to resist digestion. True absorption of calcium was shown to be lower from alfalfa hay and higher from corn silage than the values currently used by the HAF research scientists. True absorption of phosphorus from these forages was also found to be higher than the values used currently.

The exact ratio of calcium to phosphorus needed in the total ration is about 1.6 to 1.0. While deficiencies and excesses of any mineral should be avoided, several studies have shown equal performance with ratios varying from 1:1 to 4:1. In some places we recommend a ratio of approximately 1.5:1 to 2:1. High-fat diets increase fecal calcium losses through the formation of soaps and thus increase the requirements for calcium. A number of nutritionists increase the level of calcium in the total ration dry matter to about 1% when feeding high-fat diets.

Milk fever has not been a problem in every dairy herds receiving rations containing adequate amounts of phosphorus and calcium. Several studies have shown that rations narrower than 1:1 and wider than 2.5:1 tend to increase the incidence of milk fever when fed during the dry period. It seems only logical that if such rations fed during the dry period can reduce the incidence of milk fever, similar rations would be optimum during lactation.

Vitamin D is associated with calcium absorption and utilization. Since in the presence of vitamin D, calcium is absorbed more efficiently, phosphorus is also used more effectively.

While the bone stores of phosphorus are large, an inadequate supply of phosphorus in the ration will soon lead to borderline deficiencies. Such deficiencies have been identified as reduced appetite, lowered disease resistance, a decline in reproductive efficiency, poor feed utilization and increased incidence of milk fever. Since the two elements are combined in bone, the mobilization of calcium as a result of parathyroid gland actions is accompanied by the incidental mobilization of phosphorus. Therefore, if calcium is not being actively mobilized from body stores, the ruminant depends on a daily intake of phosphorus. Studies have shown that low phosphorus diets for beef heifers have resulted in decreased bone density and mineral content.

Calcium and phosphorus are important in several body functions. Calcium functions in cell equilibrium, heart beat and muscle contraction, and blood coagulation. Phosphorus is present in all living cells of the body as part of many enzyme systems and is essential in the utilization, transfer and storage of energy and in protein metabolism. Phosphorus is also necessary for normal growth and function of rumen microorganisms, especially cellulose digesters. It is also a major blood buffer.

Magnesium

Magnesium functions in many important enzyme systems in the body, as a constituent of bone, and in muscle contractions. Magnesium in the bone probably has a structural function as well as a storage function.

Grass tetany is the common condition associated with a magnesium deficiency in ruminants. Several Global locations have reported grass tetany in beef cows on wintering rations. The condition occurs more frequently in cattle grazing small-grain pastures in early spring and is usually related to low levels of blood magnesium. Supplemental feeding of magnesium to cows grazing such pastures has been very effective in preventing the tetany syndrome. Dairy cattle receiving grain in addition to such pastures have not been reported as having a problem.

High levels of nitrogen and potassium fertilization have been associated with a greater incidence of the tetany syndrome, and appear to make that magnesium which is present less available to animals. Apparently, increased production of ammonia in the rumen reduces magnesium absorption.

Some studies have reported that magnesium has a relaxing effect on animals. This is probably true to the extent that symptoms of a magnesium deficiency include hyper-irritability, increased nervousness, restlessness, muscle twitching, grinding of teeth and excessive salivation.

Supplementation of magnesium above current Global research recommendations (0.2 to 0.25% of DM) resulted in increased FCM yield. Maximum response to magnesium depended on stage of lactation. However, early lactation, high-producing cows produced maximum FCM when 0.45% magnesium was added to the diet. In general, we recommend the magnesium content of the ration be increased from 0.25% to about 0.35% of the ration dry matter during summer.

Potassium

The third most abundant mineral element in the cow’s body is potassium. Potassium plays many important roles in the body, It is involved in several enzyme systems, influences muscle activity (notably cardiac muscle), and within the cells it functions (like sodium in the extracellular fluid) by influencing acid base balance and osmotic pressure, including water retention. Potassium is a major mineral component of milk, and is also excreted in sweat, which makes it an important consideration in hot climates such as Florida.

The 1989 NRC standards suggest that the total ration dry matter for high producing cows should contain a minimum of 1.0% potassium. Under heat stress management conditions, work at HAF India shows a greater need for potassium than suggested in the 1989 NRC Update on Nutrient Requirements of Dairy Cattle. Cows receiving higher levels of potassium (1.5% dry matter) and sodium (0.5% to 0.6% dry matter) produced two more pounds of milk and appeared less heat stressed on hot days.

Most rations appear to meet minimum potassium requirements. Some ingredients, however, such as brewers’ grain, are notably low in potassium. Dairies using large quantities of wet brewers’ grain or other feeds low in potassium should consider supplementation. Most forages are quite high in potassium.

Potassium has been linked to milk fever. High levels of potassium in the diet of dry cows has been related to increased incidence of milk fever. It is recommended to limit the intake of these minerals during the dry period.

Non-specific deficiency symptoms, including slow growth, reduced consumption and efficiency, stiffness and emaciation, have been reported.

Sulfur

Sulfur is an important element in the synthesis of protein because two important amino acids, methionine and cysteine, contain sulfur. These two amino acids are prominent in protein structure and proteins are involved in practically all body processes. In ruminants, sulfur makes up about 0.15% of the body tissue and about 0.03% of milk.

Sulfur is directly related to protein and nitrogen utilization in the ruminant. It is now generally agreed among researchers that the dietary N:S ration should be about 10:1 for dairy cattle. However, basing sulfur supplementation on nitrogen:sulfur ration alone is not enough. Diets high in fiber and low in nitrogen should balance sulfur according to total sulfur content of the ration. To meet this requirement, a complete feed (90% dry matter) containing 13% crude protein should contain about 0.2% sulfur. Sources such as sodium sulfate, potassium sulfate, magnesium sulfate, ammonium sulfate and calcium sulfate are effective in meeting the requirements. Ruminant animals have an advantage over other animals as they have the ability to also utilize inorganic sulfur because of microbial reduction in the rumen. Methionine and sodium sulfate are utilized more efficiently than elemental sulfur. Retention studies show that elemental sulfur and sodium sulfate are retained about 38% and 80% as well as sulfur from methionine.

Sulfur is an important anion for close-up dry cows in the prevention of milk fever. Maximum sulfur allowance during the dry period should be between 0.40 and 0.50% of the ration dry matter.

A number of indicators of sulfur deficiencies have been reported. These symptoms are reduced feed intake, slower gains, dullness, lower digestibility, and reduced milk production.

Sodium Chloride (Salt)

Supplemental salt is needed in all current dairy cattle rations fed in Florida. It is usually added as trace mineral (TM) salt or as a packaged, complete mineral in the ration rather than feeding free-choice. A concentrate should contain about 1% TM salt (up to 1.5% with high silage rations) and a complete feed 0.5 to 1.0%. Mixing salt with the other ration components takes advantage of its condiment qualities and assures adequate intake of salt. Dry cows and heifers should have free access to salt and other needed minerals when grain consumption is limited. Salt intake to heavy springers should be limited or blended with the ration to prevent udder edema. If udder edema is a problem, reduce the sodium and potassium content of the ration. Since pasture forages are high in potassium, prepartum cows may need pasture restricted.

Sodium functions in maintaining body fluid balance, osmotic pressure regulation, and acid-base glucose and for amino acid transport and is a controlling factor in nerve transmission. Chlorine is a factor in extracellular fluid. It functions in maintaining the acid-base balance, in osmotic regulation, and in the formation of hydrochloric acid that is important to digestion in the abomasum.

The chlorine content of feedstuffs is quite variable. When sodium is supplied in the form of sodium bicarbonate or a similar source of sodium, it may be necessary to add a source of chlorine to meet the chlorine requirement. Salt is generally the cheapest source of chlorine. HAF have suggested that a diet of 0.18% chlorine is adequate for lactating dairy cows. The HAF has recommended 0.18% sodium and 0.25% chlorine to be included in the total ration dry matter. Our Works at different locations shows a greater need for sodium  especially under heat stress conditions. As a result of the Field Studies, we recommend the total diet dry matter contain 0.3 to 0.4% sodium under normal Florida conditions and 0.5 to 0.6% under heat stress conditions.

Salt deficiency causes an intense craving for salt, lack of appetite, poor growth, haggard appearance, lusterless eyes, a rough haircoat and lowered milk production. Recovery is rapid with the addition of salt to the diet.

We have been stressing the desirability of having first calf heifers calve at less than 26 months of age. Some dairymen have been resistant to this because they felt that young heifers did not do well during their first lactation relative to older heifers. One of the keys to making the system work is getting the heifer to calve at an acceptable size (at least 1200 lbs. for large breed heifers and 800 for small breeds). This is weight after the calf is born. Heifers that reach this size generally do well and have the ability to peak at 70 or more lbs. of milk per day. In order to do this, Holsteins must average about 1.7 lbs. gain/day and Jerseys 1.2 lbs. after weaning.

Table 1 contains requirements for three ages of heifers. The 3-6 month group needs more nutrients per pound of feed than the 6-12 and 12 and older groups. Younger heifers consume less feed, so the nutrient density needs to be higher. Protein required drops from 16% for the young calf to 12% for the older heifers. Virginia Tech research suggests that energy content of diets for a given rate of gain should be adjusted according to housing and environmental conditions. Heifers reared in confinement housing, such as the Virginia Countersloped barn, require 10-20% less energy. Adjust pounds of grain fed per day based on observed gain. Notice that calcium and phosphorus concentration declines as the heifer gets older, but the other minerals do not change with age. Part of this is due to a lack of information about the requirements for some of these nutrients, especially the microminerals. The vitamins are expressed as amounts (International Units) and not concentration, and they actually increase as the heifer gets older. This would be true for all of the other nutrients if actual quantity was expressed instead of concentration. These tables of nutrient requirements for heifer growth are suggestions and represent nutrients required under optimal conditions. During cold, wet weather, energy requirements increase. Similarly, heifers heavily infected with intestinal parasites require higher levels of nutrients.

Nutrient Specifications for the Dairy Herd; Table 1

Table 1. Dairy cattle ration specifications for heifers, dry cows, and lactating cows

^aHigh and low group cows are assumed to be producing 20% above or below herd average; if feeding two groups the medium group specification should be the low group. High group cows would be mature Holsteins producing 80 or more pounds of 4.0% milk, middle group would be 80 to 50 pounds, and low group below 50 pounds. Special consideration should be given to first calf heifers and smaller dairy breeds. Ranges are what would be under normal conditions, but will vary with production level of herd, environmental conditions, etc.

^bHeifers reared under confinement may need to have lower levels of energy to prevent deposition of fat in the mammary gland. Limit weight gain to 2 lbs/day or less.

^bPregnant dry cows (large breeds) in the last two months of gestation should receive at least 60 grams of calcium per day, but not more than 100 grams. At least 30 grams of phosphorus should be in the ration. Reduce by 20% for Jerseys.

Dry Cows

Dry cow requirements are to maintain the cow plus fetal growth plus some weight gain. The range in energy is to accommodate situations where some body condition restoration is needed during the dry period. Indications are that .25 to .5 body condition units can be put on during the dry period with little adverse effect. The requirements for energy are higher than NRC in an attempt to ensure acceptable condition at calving. The other nutrients are similar to NRC except vitamin E, which has a range up to 1000 IU’s, a level that has been associated with improved udder health and reduced somatic cell counts. Close-up dry cows, cows in the last 2 to 3 weeks of the dry period, usually are placed on a transition ration that contains more nutrients than would be in a ration for the far-off cows. Energy would be at the upper end of the suggested range and fiber at the lower end. Sometimes protein is also increased as more supplement is fed. If anionic salts are fed calcium is many times increased to levels greater than suggested in the table. Calcium at 1.4% of the dry matter ration has been proposed as desirable when anionic salts are fed to the close-up dry cows. Care should be taken when using these salts because of palatability problems and the elevated calcium.

Lactating Cows

The lactating cows are categorized by production group within the herd. The high production group would be those top producers in the herd plus most cows less than 90 days in milk. A range is given in order to adjust for production of the herd. Lower producing herds wouldn’t need as much as higher producing herds, because cows are not milking at as high a level. The higher producers will many times be fed fat and, therefore, the calcium should be .9-1% and magnesium .30%. Requirements for potassium, sulfur, iron, copper, manganese, and zinc have been increased above NRC for the top production group.

First calf heifers should be given special consideration and remain in the top group to a lower production level than older cows. In other words, if older cows are moved out of the top group at 80 lbs. of milk, first calf heifers might be moved at 70 lbs. because body weight is less and they have less ability to consume feed. Therefore, they need a more nutrient dense ration. Not too many herds in Virginia contain three production groups. Most usually have two groups. In this case, the middle group specifications would be appropriate for the low group. The low group’s specifications would only be appropriate with cows in the final few months of gestation, producing less than 50 lbs. of milk. Herds that are capable of having three groups will often have a high production group composed only of older cows and a separate heifer group. Both groups would be fed the high group ration. The third group would be compatible with the middle group specs. The goal is to prevent extreme changes in nutrient concentration when switching groups. This minimizes the reduction in milk when switching groups.

Table 2 contains some terms nutritionists consider when attempting to balance the ration for rumen available carbohydrates and protein. Nonfiber carbohydrates are our best indication of the carbohydrates that are available for fermentation in the rumen. In most rations much of this fraction would be starch, primarily from grains and corn silage. At the nonfiber carbohydrate levels indicated, there should be adequate energy for the rumen to produce adequate microbial protein.

Protein is divided into that which is undegradable and degradable in the rumen. These two must add up to 100%. Generally, higher production warrants higher concentration of undegradable protein. Not all the research supports this idea and it is still uncertain when a response is expected. However, many nutritionists are recommending a source of rumen resistant protein in rations for high producing cows. Neither undegradable or degradable protein can be measured with a laboratory test. Therefore, book or average values are used, making this aspect of nutrition as much art as science. A recommendation is to have half of the degradable protein as soluble. Soluble protein indicates the amount of degradable protein that is rapidly degraded in the rumen and is easily mesured in the laboratory.

Updated Nutrient Specifications for the Dairy Herd; Table 2

Table 2. Recommended nonfiber carbohydrates and rumen degradable protein in rations for lactating cows.

In the rumen, microbial digestion of cellulose and hemicellulose (from roughages) and starch (from grains) results in the production of energy rich byproducts called volatile fatty acids (VFA’s) which are absorbed by the animal through the rumen wall. This is the major source of energy for the animal. Some starch is not digested in the rumen and is passed on to the true stomach (abomasum) and small intestine where it is broken down by the animal’s enzymes and absorbed.

Rumen microbe species are specialized in their ability to break down either starch or cellulose. When the diet is high in roughages, the cellulose (fibre) digesting microbes multiply and dominate. With a high grain diet the number of starch digesting microbes increases. Changes in the composition of a ration should be made gradually to allow time for the rumen microbe population to adapt. About 2 weeks is necessary for making major changes in ration ingredients.

Grains vary in their rate of breakdown in the rumen. This is due to the chemical nature of the starch and the physical structure of the grain. For example, dry corn is degraded in the rumen much more slowly than high moisture corn or dry wheat. This has important implications for the maintenance of rumen health when feeding high grain feedlot rations.

Protein Digestion

Crude protein includes both true protein and non-protein nitrogen (NPN). The digestion of a particular protein depends to a large extent on how easily it dissolves in rumen fluid. Highly soluble protein is more likely to be broken down by rumen microbes than is insoluble protein. Nonprotein nitrogen sources (e.g. urea, ammonia) are 100% soluble in the rumen. The rumen microbes use the nitrogen released in the rumen to form their own microbial protein. Microbes are continually being moved with digesta into the lower digestive tract, where they are digested and absorbed by the animal. Most of the protein which is not soluble in the rumen (bypass or escape protein) passes unchanged to the lower digestive tract. A portion of this protein is broken down by the animal’s enzymes and absorbed. Digestible bypass protein is efficiently utilized and is an important component in rations for fast growing beef cattle.

The activity of the rumen microbes in breaking down and reforming dietary protein has important implications for the ruminant:

1. ruminants can thrive on diets containing low quality, low cost protein (relative to monogastrics) since rumen microbes upgrade the protein quality by manufacturing limiting amino acids

2. ruminants can utilize some inexpensive non-protein nitrogen (such as urea) in their diet as a protein substitute.

For optimum performance, a balance of rumen soluble protein (and NPN) and bypass protein is required. Diets with high levels of soluble protein and/or NPN may not supply adequate amounts of protein to the small intestine. Diets with high levels of bypass protein may not supply adequate amounts of nitrogen to rumen microbes for efficient microbial growth and feed digestion. Optimum diets usually contain 30-40% available bypass protein and 60-70% rumen soluble protein. Less than 30% of total protein should be in the form of NPN.

In order for rumen microbes to utilize NPN, sufficient soluble carbohydrates (e.g. starch) must included in the diet. Without adequate available energy in the diet, the capacity of the microbes to utilize NPN would be overloaded. Excess NPN will be absorbed by the animal as ammonia, and excreted. If NPN levels are high, toxicity will occur (urea poisoning).

Ration Formulation

A properly formulated ration supplies adequate amounts of all nutrients to allow cattle to achieve a desired level of production. Accurate ration formulation requires

1. precise description of the class of cattle (sex, weight, frame size, body condition, desired rate of gain, stage of production)

2. knowledge of management practices utilized (implant usage, feed additives)

3. accurate description of the nutrient content of the available feeds

Laboratory analyses of forages is essential for accurate ration formulation. The nutrient content of forages varies greatly depending on the type, stage of maturity at cutting and how well it is preserved. For more information on lab analysis see OMAF Factsheet, “Feed Sampling and Analysis” Agdex 400/60. Nutrient content of grains is not as variable as forages, but lab analysis is recommended. Help in formulating rations is available from your OMAF county office, feed industry representatives and consultants.

A knowledge of the basic digestive system of cattle and the role of various nutrients is important to beef producers. Combined with accurate feed analysis, it allows the formulation of balanced rations which will meet production goals in an economic manner. It also enhances the management of the feeding program by providing the background information necessary to prevent or resolve problem situations.